Solve "Index exceeds the number of array elements (1)", "Vectors must be the same length." errors
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sookyung Kang
on 15 Jul 2020
Commented: Walter Roberson
on 20 Jul 2020
I'd like to solve those problems from under coding using A, B, and C relationships. If equation error can't be fixed, "B(i+1)=B(i)+((h.*q)/(k*T*E))*C(i)" can be used.
a = 0;
b = 1;
n = 110;
k = 8.61733*10^(-5);
T = 300 ;
q = 1.60218*10^(-19);
E = 8.8542*10^(-12)
x= linspace(a,b,n);
h= x(2)-x(1);
A = zeros(size(x));
B = zeros(size(x));
for i = 0:n-1
A(0)=3;
B(0)=1;
C(i)=2*x(i)+3;
A(i+1)=A(i)-h.*B(i)-(0.5.*h.^2*q.*C(i))./(k*T*E);
B(i+1)=B(i)+((h.*q)/(k*T*E))*0.5*(C(i)+C(i+1));%equation error
end
plot(transpose(x),A,'.')
1 Comment
Tanmay Das
on 15 Jul 2020
Hi. Can you please try starting the index from 1 instead of 0 and go upto n in the for loop?
Accepted Answer
Walter Roberson
on 15 Jul 2020
a = 0;
b = 1;
n = 110;
k = 8.61733*10^(-5);
T = 300 ;
q = 1.60218*10^(-19);
E = 8.8542*10^(-12)
x= linspace(a,b,n);
h= x(2)-x(1);
A = zeros(size(x));
B = zeros(size(x));
A(0+1)=3;
B(0+1)=1;
for i = 0:n-1
C(i+1)=2*x(i+1)+3;
A(i+1+1)=A(i+1)-h.*B(i+1)-(0.5.*h.^2*q.*C(i+1))./(k*T*E);
B(i+1+1)=B(i+1)+((h.*q)/(k*T*E))*0.5*(C(i+1)+C(i+1+1));
end
plot(transpose(x),A,'.')
12 Comments
Walter Roberson
on 20 Jul 2020
Which theoretical equation are you comparing to, and which result from your program are you comparing it to?
How do you know when you have reached and adequate solution?
More Answers (1)
Tanmay Das
on 15 Jul 2020
Hi,
I have the understanding that you are facing trouble in indexing of arrays. Unlike C++ or Python, indexing starts from 1 in MATLAB. So if you write A(0), then it will throw error. The following code may be useful for your understanding:
a = 0;
b = 1;
n = 110;
k = 8.61733*10^(-5);
T = 300 ;
q = 1.60218*10^(-19);
E = 8.8542*10^(-12)
x= linspace(a,b,n);
h= x(2)-x(1);
A = zeros(size(x));
B = zeros(size(x));
A(1)=3;
B(1)=1;
C = 2*x + 3
for i = 1:n-1
A(i+1)=A(i)-h.*B(i)-(0.5.*h.^2*q.*C(i))./(k*T*E);
B(i+1)=B(i)+((h.*q)/(k*T*E))*0.5*(C(i)+C(i+1));%equation error
end
plot(transpose(x),A,'.')
Also please note that similar operations on each element of array can be done at once in MATLAB and do not require to run a loop like in case of C.
C = 2*x + 3
Hope that helps!
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